Stable frequency conversion system



May 13, 1947. H. DE'FRANCE 2,420,303

STABLE FREQUENCY CONVERSION SYSTEM Original Filed April 28, 1942 3Sheets-Sheet l IN VENTO f gay/w osw emvcsaq.

May 13, 1947- H. DE FRANCE STABLE FREQUENCY CONVERSION SYSTEM OriginalFiled April 28, 1942 INVENTOR HENRI DE FRANCE xv Q5 xv MN W M y 13,1947- H. DE FRANCE 2,420,303

STABLE FREQUENCY CONVERSION SYSTEM Original Filed April 28, 1942 5Sheets-Sheet 5 0, v a? ,V

Amp/vans Patented May 13, 1947 STABLE FREQUENCY CONVERSION SYSTEM Henride France, Lyon, Rhone, France; vested in the Attorney General of theUnited States Continuation of application Serial No. 440,860, April 28,1942. This application November 6, 1942, Serial No. 464,750. In FranceMarch 12,

12 Claims.

The present invention relates to oscillation generating systems for usein connection with television and like apparatus. The presentapplication is a continuation of my prior application Serial No.440,860, filed April 28, 1942.

An'object of the invention is to provide oscillation generator systems,with means and methods for the adjustment thereof, which are especially,although not exclusively, applicable to apparatus for the transmissionof television picture and line signals, such systems being more stable,and better adapted to meet the requirements of practice than those usedfor the same purpose up to the present time.

According to a feature of the present invention, in systems of thefrequency demultiplier type, that is to say systems including aplurality of oscillators cooperating together so as to supply at leasttwo utilization frequencies affording a given ratio of demultiplicationor multiplication, I have recourse, in order to adjust the frequenciesof the various oscillators, to means adapted to act simultaneously onthose of their respective elements upon which the successive frequenciesthat are produced depend, in a manner to positively maintain the ratiosof said frequencies, and, in particular, I impress perfectly determinedand adjustable voltages upon said elements, for instance by means of apotentiometer common to the various oscillators.

According to another feature of the invention, pertinent to systems ofthe type above referred to, for producing at least one given frequency,especially those for television picture and line signals, I superimposeon this frequency a standard frequency (for instance that of analternating current distribution system), and I cause the resultantfrequency to react (preferably after detection) on the elements of saidsystem upon which depends the frequency to be produced.

Another object of the present invention is the provision of a frequencydemultiplier or multiplier which maintains the frequency conversionratio in a more accurate manner than in the systems used for the samepurpose up to the present time.

With this last mentioned object in view, according to a feature of myinvention, I have recourse to a series of oscillators connected to oneanother according to multiples or sub-multiples of the fundamentalfrequency, their oscillations being preferably of the saw teeth type inorder to increase the accuracy of the synchronism, and I combine withsuch an assembly means for controlling the frequency conversion ratio,such 2 means including at least one oscillograph whose series of platescan be coupled at will selectively with at least two of the oscillators,in a manner to render visible the synchronism, according to theappearance of the resultant curve.

Other features of the present invention will be evident from thefollowing detailed description and the drawings wherein preferredembodiments of the invention are given by way of example.

Fig, 1 is a diagram of a system for the transmission of synchronisationsignals for television, according to the invention;

Fig. 2 is a curve illustrating the saw-tooth voltage supplied by thefirst stage of the system of Fig. 1 and the frequency of which is tocorrespond to that of the line signals;

Fig. 3 is a curve similar to that of Fig. 1 illustrating the productionof the picture synchronizing signals obtained at the output end of thesystems;

Fig. 4 is a curve illustrating the voltage of an alternating currentdistribution system to be superimposed, according to a feature of theinvention, on the picture synchronizing signals produced by a system ofthe kind of Fig. 1;

Fig. 5 is a similar curve illustrating the result of thissuperimposition of voltages;

Fig. 6 diagrammatically shows the whole of a line and picture frequencygenerating system for use in television, and of a device for the controlof the frequencies, according to the invention;

Fig. 7 diagrammatically shows the relaxation tubes which can'advantageously be used in such a combined system according to thepresent invention;

Fig. 8 is a view, similar to Fig. 7, showing similar tubes madeaccording to a modification.

I will first describe a system according to the invention for theproduction of oscillations for 40 transmitting synchronizing signals(corresponding to pictures and lines) for television.

It is known in the art to make use, for this transmission, of a seriesof multivibrators or relaxation oscillators the first of which suppliesthe frequency which is to correspond to the scanning of the lines (forinstance 441 =22050, if it is desired to obtain 441 lines in eachpicture and 50 pictures per second) while the others are synchronized tofrequencies which are sub-mul- 50 tiples of the first, so as finally tosupply the frequency of the picture synchronizing signals, to wit 50 persecond.

For instance, in a given arrangement, the system includes, after thefirst oscillator, tuned to the frequency of 22,050 per second, fouroscil- 3 lators respectively synchronized to the following frequencies:

However, this kind of arrangement involves disadvantages. In particular,if the frequency of the first oscillator varies by a value equal to ofits value, due for instance to a voltage adjustment, the secondoscillator suddenly ceases to correspond to the sub-harmonic of order 7so as to correspond to the adjacent sub-harmonic of order 6 or 8,whereby the Scanning is wholly modified. In order to obviate thesedrawbacks, according to the invention the respective oscillators arecaused to coact with regulating means such that 150; and 50 theypositively maintain the ratiosbetween the successive frequencies.

For instance, if the frequency of each of said oscillators depends uponthe discharge speed of a condenser, as is the case with oscillators ormulti-vibrators of the relaxation type, this speed being itself afunction ofa voltage impressed, for instance, upon one of the electrodesof thetube or of one of the tubes of the corresponding oscillator, theregulating will consist in regulating the above mentioned voltages ofthe respective oscillators from a common device, such for instance as apotentiometer.

It goes without saying that such a result can be obtained in manydifferent manners depending inparticular upon thenature of theoscillators that are utilized.

In Fig. 1, I have shown a group of multivibrators or relaxationoscillators, of known types, the first two oscillators only being shownon the drawing.

Compartment I contains the main oscillator. Condenser I dischargesslowly into pentode tube 2, and it is charged suddenly through tube 3during the short time for which the latter is not fully blocked by itspolarization. An auxiliary tube 4 may be provided, inknown manner, foraccelerating the beginning of the charge. Finally,

.the discharge speed, which determines the fre- Such a system havingbeen provided, it is then combined, as above stated, with a commonadjustment potentiometer, through which the individual potentiometers 5,5', etc. are fed, instead of having them controlled, in the usualmanner, by the high frequency of the station.

It will be readily understood that with this adjustment common to thevarious compartments, it is possible simultaneously to vary therespective discharge of condensers I, I', etc., by

. proportional amounts, which also ensures proquency, is initiallyregulated through any known 7 means, for instance by adjusting thescreen voltage of tube 2, which determines the value of the platecurrent. This adjustment is efiected by means of a potentiometer 5 orthrough any other means.

Finally, I obtain, at the output end of the first compartment, at A, avoltage which has, for instance, the saw-tooth shape illustrated by Fig.2 and which is utilized for the line synchronizing signals, itsfrequency having been suitably adjusted for this purpose.

Compartment II, which is connected to the first compartment through acapacity or other coupling, includes elements I, 2, 3, 4', similar tothose of the first compartment. However, the capacity of condenser I isgreater in such manner as to supply a lower frequency, with thedemultiplication ratio that has been chosen. Furthermore, in order totransmit the voltage of compartment I, there are provided means such asa tube 6 or the like for ensuring synchronizing, by frequencydemultiplication, of compartment II with compartment I.

Compartments III, IV, etc., in turn supply demultiplied frequencies. Thelast one produces, at its output end, at B, a voltage at the frequencyof the picture synchronizing signals, for instance per second and in 'aform illustrated by the curve of Fig; 3.

portional displacements of all the intermediate frequencies of thesystem.

Thus is ensured the maintaining of the ratio of the extreme frequencies,but it should be well understood that all other assemblies giving thedesired result might be employed according to the invention.

With such a system as described above there can be advantageously usedother features such as the following, which can be employed separatelyif desired.

According to one of these features, which will be supposed to be appliedto a system of the type above described, I have recourse, forstabilizing the frequencies generated by said system, to means utilizingthe superimposition of a standard frequency for reacting, in a suitablemanner, upon the elements upon which depend the value of saidfrequencies.

Thus, considering the voltage of the picture synchronizing signals,obtained at the output end of the system at B, which, in the examplethat has been chosen, varies at a frequency which is supposed to be of50 periods,

a. there is imposed on to this voltage, by means of a suitable mixingdevice 8 of a known type, the alternating sinusoidal voltage of adistribution system I4 of 50 periods frequency (Fig. 4), thissuperposition giving rise to a combined voltage as illustrated by Fig.5;

b. there is effected, through any suitable means, a detection of thetops of the curve of this resultant voltage in such a way that aconstant rectified continuous voltage is produced, if both of thecomponent frequencies remain the same, while a variable voltage isproduced if dephasings take place due to variations between these twofrequencies, and

c. the voltage that is obtained is caused to act upon at least one ofthe compartments I, II, etc., or upon each of these compartments,through one of the elements upon which the frequency depends, forinstance the control grids of tubes I,

I, etc., as shown by the drawing.

In the example illustrated by the drawing,

detector 9 includes a diode tube II] and the negative rectified voltageII is utilized for polarizing the control grids, with suitable couplingsshown at I2, I2, etc., the whole being arranged in such manner that aneffect is produced upon the discharge speed of condensers I, I, etc., ina correcting direction, that is to say in such manner as to bring thefinal frequency of signal B to a value equal to that of the distributionsystem.

In order to obtain this result, if the signals succeed one another attime intervals shorter than desired, the discharge speed of I isreduced, by producing increased polarization of tube 2 corresponding toan increase in the absolute value of negative voltage I'I. Examinationof Fig. 5 shows that this is what takes place when the signals tend tomove toward the left, since the maximum ordinate of their tops thentends to I increase.

It is known that, in a television system, it is necessary to obtain avery sharp synchronism relation between the two extreme frequencies,that is, the frequency of the lines and the frequency of the pictures,the second of which must be, very accurately, a sub-multiple of thefirst. Accuracy of synchronism is especially important with theinterlacing method, the efiiciency of which is wholly nullified if theend of a picture, for instance, is not obtained for exactly the sameposition of a line of a given number.

According to a feature of the present invention, in order to obtain thedesired synchronism, the whole of the oscillator system is firstarranged in such manner as to include a fundamental generator coupledwith a series of generators of proper sub-multiple frequencies, whichare interrelated to one another, as above described.

These generators are preferably such that they supply a saw-tooth curve,because such an arrangement permits of increasing the accuracy and thestability of the interrelation between the generators, and therefore thesynchronism.

It suffices to utilize for this purpose any known device, of therelaxation or other type, with ordinary tubes mounted as multivibratorsor thyratrons.

If for example, it be desired to obtain, in the interlacing method, ananalysis corresponding to 441 lines and 50 half pictures per second(therefore 25 complete pictures per second) I may make use of afundamental generator C (Fig. 6) giving a frequency of:

f=441 50=22,050 cycles and to which are successively connectedgenerators D, E, F, G; giving the following sub-multiple frequencies:

as shown at C on Fig. 6.

In Figs. 7 and 8, I have shown, merely by way of example, two mountingsinvolving to the use of thyratrons.

According to the embodiments of Fig. 7, the synchronizing signals comingfrom the preceding generator are applied to the grid of thyratron Uthrough a condenser 3|. The leak resistance is shown at 32 and theadjustable resistance at 33. The plate of the thyratron which isconnected with high voltage HT through an adjustable resistance, returnsto the ground through a condenser V. The cathode circuit is positivelypolarized. The saw-tooth signals coming from said plate (anddiagrammatically shown on the drawing) are then transmitted through acondenser 34 to the grid of a tube 35 which feeds, with the usual phasedifference of a sawtooth current (also shown in the drawing). Thesesignals are finally transmitted to the next generator and so on.

Fig. 8 shows an analogous system in which the same reference numeralsdesignate the same elements. The only difference lies in the fact thatthe signals, indicated on the drawing, result from the practicallyinstantaneous charge and discharge of cathode U. By using preferably inthe cathode circuit a resistance R, I obtain in said circuit very shortsignals (top of Fig. 8) corresponding to the successive discharges ofcondenser V. These signals are utilized for synchronizing the nextgenerator.

Such systems produce saw tooth curves of very sharp shape which are welladapted to the desired purpose.

With a series of such generators or any analogous arrangement, I combinemeans for checking the accuracy of the synchronism, that is to say thedemultiplication, which means are constituted by at least one cathodeoscillograph whose plates or series of plates may be coupled at willwith at least two of the various generators. I can thus render visiblethe synchronism that is obtained, in accordance with the aspect of theresultant curve shown in said oscillograph.

For instance, considering such an oscillograph 0 (Fig. 6) and supposing(also by way of example) that two of the plates of said oscillograph aregrounded, it will be seen that if the two other plates are respectivelyconnected to generators C and D, I obtain on the screen of theoscillograph a Lissajou curve which, when the demultiplication isensured in an exact manner, must be constituted by seven teeth, forinstance, in the horizontal direction (that is to say with sharpvertical ridges).

If now, without modifying the connection between generator D and thecorresponding deviating plate, I connect the other plate to generator E,I must obtain, under the same conditions, a resultant curve having seventeeth, in the vertical direction.

Of course, it is advantageous, in order to permit of working quickly, tomake use of a switch such as a, including a suitable number of contactpoints, for instance three, if it is desired to be able to check thesynchronism between C and 0', when a generator such as C has beenprovided.

The same checking operation can be performed with the followinggenerators such as E, F, G, and this either with another oscillograph Oas shown, or by means of the same oscillograph O associated with theswitch a including a suitable number of contact points.

In any case, whatever may be the particular embodiment that is finallychosen, I obtain a system whose operation is sufficiently clear from theforegoing disclosure to make it unnecessary to enter into furtherdetails.

This system compared with prior systems used for the same purpose, hasthe following advantages:

(a) It ensures an easy, quick and very exact checking of thedemultiplication ratio, that is to say of the synchronism; and

gators-3 lit renders'thatfsynchronism more'effective, owi gto'the'saw-toothsha'pe of the oscillations,

which permits of connecting the various generators with one another in asafe manner.

7 Of course, l may utilize supplementary syn- I cially intended'fortelevision, which'comprises, in

combination, at least two oscillator devices, each oscillator deviceincluding a potentiometer determining the frequency of the oscillationsproduced by such device, coupling means interconnecting said'o'scillatordevices so that the frequency of one depends upon the frequency of theother, and a common potentiometer for applying a potentialsimultaneously to the potentiometers of the oscillator devices tosimultaneously regulate the frequencies of said oscillator devic'es,'andthereby positivelymaintain the desired ratio of said frequencies. 7 l

2. A system for'generating oscillations, 'especially intended fortelevision, which comprises, in combination, at least two oscillatordevices, each oscillator device including an element determining thefrequencyof the oscillations produced by such device, meansinterconnecting said oscillator devices so that the frequency of onedepends upon the frequency of the other, a common means for applying apotential simultaneously to said elements of the oscillator devices tosimultaneously regulate the frequencies of said oscillator devices, andthereby positively maintain the desired ratio of said frequencies, meansfor superimposing a'stan'dard alternating voltage on the voltageobtained atthe output of the final oscillator device, means for:detecting the tops of the curve corresponding to the superimposedvoltages, and means for causing the voltage thereby obtainedto act on atleast one 7 of said'oscillator devices. 1

3 A system for generating oscillationsjespecially intended fortelevision, which'coniprises, in combination, at least two oscillatordevices, each oscillator device including an element "determining thefrequency-of thebscillations produced by such device, couplingmeansinterconnecti'ng said oscillator devices so that the-frequency ofone depends uponthe frequency of thelother, a common potentit'mietersimultaneously applying a 'pote ntialto 5 said elements fof theoscillator devices to simultaneously, regulate the frequencies ofsaidfoscillator"devices, and

thereby positively to maintain the desired ratio iof said frequencies,means for-superimposing a standard alternating voltageon the voltageobtainedat the output of the final oscillator device,

means for detecting jthe to ps of curvecorresponding to the superimposedvoltages, and means for causing the voltage' -therebyobtained to act onat least one of said oscillator devices.

4. A system for'generating oscillations, especially intended fortelevision, whichcomprisesjin combination at least two oscillatordevices, each oscillator device including apcteniometer deter mining thefrequency of'the' oscillations produced by such device, coupling meansinterconnectin said oscillator devices so that the frequency of onedepends upon the frequency of the other, a common potentiometer forapplying a potential simultaneously to said potentiometers of theoscillator devices to simultaneously regulate the frequencies of saidoscillator devices, and thereby positively maintain the desired ratio ofsaid frequencies, means for superimposing a standard a1- ternatingvoltage on the output of'final oscillator device, means for detectingthe tops of the curve corresponding to the superimposed voltages, andmeans for causing the voltage thereby obtained to acton at least one ofsaid oscillator devices.

5. A system for generating oscillations especiall intended fortelevision, which comprises, in combination at least two oscillatordevices, each oscillator device including a pentode tube, another tubearranged to be periodically polarized, a condenser connected with saidtubes in a manner to slowly discharge through the firstmentioned tubeand to be suddenly charged through the second mentioned tube when thelatter is not blocked by polarization, an auxiliary tube connected in amanner to accelerate the beginning of the charge of the condenser, andadjusting means connected with the screen of thefirst mentioned tube foradjusting the screen voltage thereof, so as to determine the platecurrent thereof, means for coupling the oscillator devices, therespective condensers of the oscillator devices being of differentcapacities so as to obtain the desired ratio of frequencies of saidoscillator devices, means for transmitting the voltage from one of theoscillator devices to the other, and a single means for feedin apotentialto said means for adjusting the screen voltages of the firstmentioned tubes'ofsaid oscillator devices.

6. A system for generating oscillations especially intended fortelevision, which comprises, in combination, at least two oscillatordevices, each oscillator device including a pentode tube, another tubearranged to be periodically polarized, a condenser connected with saidtubes in a manner to slowly discharge'through the first-mentioned tubeand to be suddenly charged through the second mentioned tube when thelatter is not blocked by polarization, an auxiliary tube connected in amanner to accelerate the beginning of the charge of the condenser,potentiometers connected with the screen of each of the first mentionedtubes for adjusting'the screen voltages thereof, so as to determinetheplate currents thereof, coupling means for connecting the'firstoscillator device with the second, the condensers of these oscillatordevices being chosen of different capacities so as to obtain the desiredratio of the respective frequencies of said oscillator devices, meansfor transmitting the voltage from the first oscillator device to thesecond, and a single adjustable means for feeding the potentiometers foradjusting the screen voltages of j the first mentioned tubes of saidoscillator devices.

{7. A system for generating oscillations especially intended fortelevision, which comprises, in combination, at least two oscillatordevices, 'each' oscillator device including a'pentode tube, another tubearranged to be periodically polarized, a condenser connected with saidtubes in a manner to slowly discharge through the first mentioned tubeand to be suddenly charged through thefsecond mentioned tube when thelatter is not blocked by'polarization, an auxiliary tube connected toaccelerate the beginning of the charge of the condenser, potentiometersconnected with the screen of each of the first mentioned tubes foradjusting the screen voltages thereof, so as to determine the platecurrents thereof, coupling means. for connecting one of the oscillatordevices with the other, the respective condensers of these oscillatordevices being chosen of different capacities so as to obtain the desiredratio of the respective frequencies of said oscillator devices, meansfor transmitting the voltage from the one oscillator device to theother, and a single potentiometer for feeding the potentiometers foradjusting the screen voltages of the first mentioned tubes of saidoscillator devices.

8. A system for generating oscillations especially intended fortelevision, which comprises, in combination, at least two oscillatordevices, each oscillator device including a pentode tube, another tubearranged to be periodically polarized, a condenser connected with saidtubes in a manner to discharge through the first mentioned tube and tobe suddenly charged through the second mentioned tube when the latter isnot blocked by polarization, an auxiliary tube connected to acceleratethe beginning of the charge of the condensers, a potentiometer connectedwith the screens of each of the first mentioned tubes for adjusting thescreen voltages thereof, so as to determine the plate currents thereof,capacities for coupling the first oscillator device with the second, therespective condensers oi the oscillator devices being chosen ofdifferent capacities so as to obtain the desired ratio of the respectivefrequencies of said oscillator devices, a tube for transmitting thevoltage from the first oscillator device to the second, and a singlepotentiometer for feeding a potential to the potentiometers provided foradjusting the screen voltages of the first mentioned tubes of saidoscillator devices.

9. A system for generating oscillations especially intended fortelevision, which comprises, in combination, at least two oscillatordevices, each oscillator device including a pentode tube, another tubearranged to be periodically polarized, a condenser connected with saidtubes in a manner to discharge through the firstmentioned tube and to besuddenly charged through the second mentioned tube when the latter isnot blocked by polarization, an auxiliary tube connected to acceleratethe beginning of the charge of the condensers, adjusting means connectedwith the screens of the first mentioned tubes for adjusting the screenvoltages thereof, so as to determine the plate currents thereof,coupling means for connecting the first oscillator device with thesecond, the respective condensers of these oscillator devices beingchosen of different capacities so as to obtain the desired ratio of therespective frequencies of said oscillator devices, means fortransmitting the voltage from the first oscillator device to the second,a single means for feeding a potential to the means provided foradjusting the screen voltages of the first mentioned tubes of saidoscillator devices. means for superimposing a standard alternatingvoltage on the output of the final oscillator device, means fordetecting the tops of the curves corresponding to the superimposedvoltages, and. means for causing the voltage thereby obtained to act onat least one component of the oscillator devices.

10. A system for generating oscillations espe- 10 cially intended fortelevision, which comprises, in combination, at least two oscillatordevices, each oscillator device including a pentode tube, another tubearranged to be periodically polarized, a condenser connected with saidtubes in a manner to discharge through the first mentioned tube and tohe suddenly charged through the second mentioned tube when the latter isnot blocked by polarization, an auxiliery tube connected to acceleratethe beginning of the charge of the condenser, potentiometers connectedwith the screens of the first mentioned tubes for adjusting the screenvoltages thereof, so as to determine the plate currents thereof,coupling means for connecting one of the oscillator devices with theother, the respective condensers of these oscillator devices beingchosen of difierent capacities so as to obtain the desired ratio of therespective frequen cies of said oscillator devices, means fortransmitting the voltage from one oscillator device to the other, asingle means for feeding the potentiometers provided for adjusting thescreen voltages of the first mentioned tubes of said oscillator devices,means for superimposing a standard alternating voltage on the voltage ofthe signal obtained at the end of the final oscillator device, means fordetecting the top of the curves corresponding to the superimposedvoltages, and means for causing the voltage thereby obtained to act onat least one component of the oscillator devices.

11. A system for generating oscillations especially intended fortelevision, which comprises, in combination, at least two oscillatordevices, each oscillator device including a pentode tube, another tubearranged to be periodically polarized, a condenser connected with saidtubes in a manner to slowly discharge through the first mentioned tubeand to be suddenly charged through the second mentioned tube when thelatter is not blocked by polarization, an auxiliary tube connected toaccelerate the beginning of the charge of the condenser, potentiometersconnected with the screens of the first mentioned tubes for adjustingthe screen voltages thereof, so as to determine the plate currentsthereof, coupling means for connecting one of the oscillator deviceswith the other, the respective condensers of these oscillator devicesbeing chosen of difierent capacities so as to obtain the desired ratioof the respective frequencies of said oscillator devices, means fortransmitting the voltage from one oscillator device to the other, asingle potentiometer for feeding a potential to the potentiometersprovided for adjusting the screen voltages of the first mentioned tubesof said oscillator devices, means for superimposing a standardalternating voltage on the output of the final oscillator device, meansfor detecting the tops of the curves corresponding to the superimposedvoltages, and means for causing the voltage thereby obtained to act onat least one of the oscillator devices.

12. A system for producing oscillations which comprises, in combination,a plurality of oscillator devices interconnected with one another sothat the frequency of one depends upon the frequenc of the precedingone, at least one oscillograph, means coupling the plates of said0scillograph with at least two of said oscillators, means forsuperimposing a standard alternating voltage on the output of the finaloscillator de vice, means for detecting the tops of the curvecorresponding to the superimposed voltages, and

11 means for causing the voltage thereby ubtained to act on at least oneof the oscillator devices.

HENRI m: FRANCE.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 12 UNITED STATES PATENTS Name Date Varian June 17, 1941 Pooh Aug.27, 1940 Puckle Apr. 19, 1938 Schlesinger eta1. Oct. 3, 1939 McCrearyOct. 30, 1934

